Afterimages

Instructions:

Focus on the middle stripe of this flag for 20-30 seconds. Try not to
blink. Then move your mouse so that the cursor moves onto the flag. This
will the background to go white and you should see the flag of the USA in
the correct colors. Sometimes it helps to blink once or twice after the
background changes.

What's Happening: in the retina of your eyes, there
are 3 types of color receptors (cones) that are most sensitive to either
red, blue or green. When you stare at a particular color for too long,
these receptors get "tired" or "fatigued.". After looking at the flag
with the strange colors, your receptors that are tired do not work as
well. Therefore, the information from all of the different color receptors
is not in balance. Therefore, you see different color "afterimages"...in
this case I have used the "mirror" colors so you see the proper colors in
the afterimage. You can also see that your vision quickly returns to
normal since the afterimage does not last for more than about 5 seconds.